A TECHNIQUE TO PREPARE GaAs VCSEL SAMPLE USING A TRIPOD POLISHER FOR TRANSMISSION ELECTRON MICROSCOPIC ANALYSIS
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2002-Jun-13
Transmission electron microscope (TEM) has been used for high resolution imaging of semicon- ductor lattice structures. It's also an effective tool in failure mode analysis (FMA) to identify defect origins and failure mechanisms. The most time-consuming part of the TEM work is sample preparation. The procedure to prepare a bulk or a blank film TEM sample typically includes grinding, polishing, dimpling and ion milling. The same method does not work well if a particular failure site needs to be analyzed in a device. To precisely pinpoint a failure site, focused ion beam machine (FIB) is a conve- nient and efficient tool to use for the TEM sample preparation, but this approach requires an expensive initial capital investment and a high cost long term maintenance. There are also concerns that the high energy ion beam will cause undesired damage to the sample, causing artifacts difficult to resolve from what is to be analyzed. An alternative way of sample preparation to analyze a specific site in a device is the so-called tripod polishing method originally developed by a group of IBM researchers. The wedged sample is prepared by polishing using different grid size diamond films and diamond suspension in succession. Sometimes, blank ion milling is used in the final step for cleaning. This technique has been successful in preparing silicon based device samples, but has encountered difficulty in preparing GaAs material based samples.